The process of obtaining a biological or other fluid sample, such as blood, and the subsequent centrifugation process generally requires multiple steps and devices, which include transferring the sample from the sampling syringe to a separate centrifugation tube, centrifugation of the sample and then decanting the separated portions to different vessels for further processing. The increase in handling time by medical personnel and the use of multiple devices, as opposed to a single device, increases the overall inconvenience, costs and time necessary to perform the procedure. More importantly, the increase in sample handling increases the risk of contaminating the sample thus, increasing the risk of contaminating later process steps-e.g., contaminating the sterile operating field wherein the contaminated plasma would be used. Furthermore, the increase in handling increases the exposure of medical personnel to whatever infectious agents the blood sample may contain.
Common prior art collection-separation-transfer systems generally use multiple devices for sample collection, separation and transfer of the plasma portion. For example U.S. Pat. No. 3,654,925 discloses using a vacuum tube to collect the sample; centrifuging the sample in a cell-collection tube coupled to the vacuum tube via an intermediate needle assembly; and transferring the plasma portion using a non-sterile syringe with a needle. The device disclosed in the '925 patent also does not allow precise transfer of all of the plasma from the separated blood sample. Another example, U.S. Pat. No. 3,586,064, discloses collecting the sample in a vacuum tube; centrifuging the vacuum tube to separate the sample; opening the vacuum tube to the atmosphere; collecting the plasma portion with a separate collection device, also opened to the atmosphere; and transferring the plasma from the collection device with a separate syringe. In both of these examples multiple steps and devices are required to accomplish sample collection, sample separation and transfer of the plasma portion. Neither example discloses an apparatus or method to precisely, controllably and aseptically transfer the entire plasma portion of the separated sample. Furthermore, neither example discloses an apparatus or method to transfer the fluid from a non-sterile environment to a sterile environment without performing an additional fluid transfer step.
Metered transfer syringes also exist in the prior art and generally, allow repetitive and accurate withdrawal and transfer of an aliquot from a bulk source. For example, U.S. Pat. No. 4,744,955 to Shapiro discloses a spring biased plunger assembly disposed within an adjustable syringe barrel assembly. The adjustable syringe barrel assembly is a hollow cylinder and a standard syringe barrel axially aligned and retained together by complementary screw threads. The spring biases against the plunger assembly which forces the plunger assembly out of the syringe barrel a fixed distance. The volume of the aliquot is controlled by relative rotation of the syringe barrel and cylinder. These metering syringes, exemplified by the '955 device, require multiple devices to accomplish sample collection, sample separation and aseptic transfer of the plasma portion of a blood sample. Due to the arrangement of the plunger and spring, such a device cannot be effectively centrifuged to allow for the ejection of the plasma fraction.
Use of the plasma portion in a sterile operating field necessitates that the collection, separation and transferring steps occur without contaminating the sample, plasma or transferring vessel. However, prior art systems have not achieved the simplicity in processing, as contemplated herein, while maintaining the necessary aseptic conditions.